Translate _articles/uk-UA/code-of-conduct.md

[webknjaz]

• Copy _articles/en-US/code-of-conduct.md to _articles/uk-UA/code-of-conduct.md and commit it
• Translate _articles/uk-UA/code-of-conduct.md contents
• Create a PR [WIP] Translate "best practices for maintainers" article #19
• Iterate over the review process